I habitually sip little and often whilst running- about 1 sip per km, more if very hot. If there is electroylte drink ( as long as it's not lucozade sport) I woudl think of using it on a hot half if you're going to be more than 2 hours.
As far as finishing goes- do you have results from last year? What is th etime limit for your race? How long did ut take you to do the 9miles? - if you have to run/ walk the rest, will you make it?
And finally- do not fear coming last- I did it once, and got a hero's reception when I got to the end ( perhaps because they could finally get away, but whatever!)
Tailwind, plus crisps, clif bars, ginger beer, and percy pigs. On a long ultra I might also add more substantial savouries like mini pork pies, cheese, and those baby food things ( preferably cheesy pasta- type, or apple, avoid anything with cauliflower, it repeats on you!).